This invention relates to a repair unit for use in the repair of injuries to vehicle tires of either the tube or tubeless type. More particularly, it is designed for reinforcing damaged pneumatic tire casings in which the injury may be of relatively large size thus requiring a repair unit which will cover a relatively large section of the surface area on the interior of the tire surrounding the injury.
Tire repair units of this general type comprising a plurality of rubberized cord plies have been heretofore designed for this specific repair function. Examples of such previously known repair units are disclosed in U.S. Pat. Nos. 2,852,058 issued Sept. 16, 1958 to F. H. Chambers, et al; 3,004,580 issued Oct. 17, 1961 to F. H. Chambers, et al and 3,036,620 issued May 29, 1962 to F. H. Chambers, et al. Each of these patents illustrates various configurations and constructions employed in the fabrication of such multi-ply tire repair units. In general, these prior art repair unit constructions employ a plurality of strips of the rubberized cord plies that are oriented in essentially a 90.degree. angular relationship to each other. Each of the plies comprises a plurality of fibrous cords that are arranged in parallel relationship to each other and formed into a single layer that is embedded into a rubber matrix. Usually, the rubber matrix is vulcanized and a layer of uncured rubber without any reinforcing cords is placed over the entire general surface of the repair unit. Thus, when the tire repair unit is applied to the interior surface of a pneumatic tire casing, the uncured rubber is placed adjacent the tire casing and on application of heat, it is also cured and serves to bond the rubberized cord plies to the tire casing.
One distinctive constructional feature that is characteristic of these prior art tire repair units is that each of the plies is of a generally rectangular shape with all of the cords in a particular ply being of the same length. Thus a tire repair unit, as applied to a casing, will have the several plies oriented so as to align with the cords in the tire casing, and presents a generally cross shaped configuration as between the several plies. Generally, the lengths of each ply are substantially greater than their widths and thus there are relatively long tab portions that extend, or project, a distance laterally with respect to the next adjacent or crosswise oriented ply.
A difficulty encountered with such tire repair unit constructions is that the endmost portions tend to first develop cracks in the rubberized plies as between the cords embedded therein and results in separation of the plies from the tire casing. This problem was recognized and thus the structure shown in U.S. Pat. No. 3,004,580 was developed and considered an improvement over the structure of a basic tire repair unit of this type as shown in U.S. Pat. No. 3,036,620. The improvement in U.S. Pat. No. 3,004,580 was the application of a strip of fabric having filaments extending in relatively crossed relationship and applied to the terminal end portions of each of the plies. This added fabric strip was positioned to extend a distance outwardly from the end of a cord ply and this outward extending portion would thus be bonded by the underlying cushion layer of rubber to the tire casing during the vulcanizing process. This fabric strip tended to reduce the likelihood that there would be breaking and separation of the rubber matrix between the respective cords in a ply and thereby prevent the ply from pulling away from and separating from the tire casing.